Refrigerant compressor

ABSTRACT

Refrigerant compressor, comprising an electric drive unit ( 2 ), a cylinder housing ( 1 ), a crankshaft ( 11 ) which may be driven by the electric drive unit, wherein the cylinder housing ( 1 ) has the main bearing for the crankshaft ( 11 ), and a piston ( 12 ), driven by the crankshaft ( 11 ) and guided in the cylinder housing ( 1 ), which compresses the refrigerant. To allow the main bearing length to be dimensioned as large as possible, it is provided that at least one height compensation element ( 26 ) is situated between the cylinder housing ( 1 ) and the electric drive unit ( 2 ) in order to keep an overall height of the cylinder housing and the respective drive unit practically identical within a compressor family having drive units of different heights.

FIELD OF THE INVENTION

The present invention relates to a refrigerant compressor comprising an electric drive unit, a cylinder housing, a crankshaft which may be driven by the electric drive unit, and a piston, driven by the crankshaft and guided in the cylinder housing, which compresses the refrigerant.

The present invention further relates to a family of refrigerant compressors of different refrigerating capacities, each refrigerant compressor comprising an electric drive unit, a cylinder housing, a crankshaft which may be driven by the electric drive unit, and a piston, driven by the crankshaft and guided in the cylinder housing, which compresses the refrigerant, wherein the electric drive unit of each refrigerant compressor in the family has a different height, depending on the refrigerating capacity.

BACKGROUND INFORMATION

Such refrigerant compressors are well known, and are used primarily in household applications such as refrigerators or freezers, for example. Refrigerant compressors are situated in a hermetically sealed outer housing, and are part of a refrigerant circuit in which the refrigerant compressor compresses a gaseous refrigerant which is supplied from an evaporator to the piston/cylinder unit. The pressure and temperature increase during the compression. As a result, the refrigerant is converted to the liquid state in a condenser and is ultimately supplied by an expansion valve to the evaporator, where it is re-evaporated. The heat of vaporization necessary for this purpose is withdrawn from the surroundings, i.e., a cooling chamber, which is thereby cooled. Lastly, the gaseous refrigerant is supplied once again from the evaporator to the piston/cylinder unit and goes through a new compression and expansion cycle.

Depending on the requirements, such refrigerant compressors are offered with different refrigerating capacities. The component which essentially determines the refrigerating capacity of a refrigerant compressor is the electric drive used. The greater the refrigerating capacity, the greater the height of the electric drive used. However, the displacement and thus the piston size vary as well as the stroke itself, and therefore contribute to differing refrigerating capacities.

The overall height of a refrigerant compressor is essentially determined by the height of the electric drive unit and the height of the cylinder housing mounted on the electric drive unit. Whereas the height of the cylinder housing is generally kept constant and only the cylinder diameter and the cylinder stroke vary slightly as a function of the refrigerating capacity, the height of the electric drive unit varies greatly as a function of the refrigerating capacity. The electric drive unit is generally a single phase asynchronous motor composed of a rotor and a stator together with winding stacks, the stator being designed as a core stack which greatly influences the height of the electric drive unit, as described in greater detail below.

The refrigerant compressor itself is situated in a hermetically sealed outer housing having an entering suction line which conducts the refrigerant to the cylinder, and an exiting pressure line which delivers the compressed refrigerant to the condenser. Also located on the hermetically sealed housing is a connecting flange for electrical lines for supplying the drive unit inside with power.

An oil sump for lubricating the moving parts of the refrigerant compressor is situated at the base of an operation-ready outer housing. Oil is conveyed to the lubrication points as a result of the rotation of the crankshaft itself, which for this purpose has two sections provided with different oil conveying means (oil conveying spindle, eccentric borehole).

A number of refrigerant compressors having numerous identical components is referred to as a “compressor family.” The individual members of a compressor family differ from one another by virtue of the refrigerating capacity and/or the efficiency, and, primarily as the result of the electric drive unit used, outer housing, crankshaft, cylinder housing, etc., are thus identical or practically identical (exceptions: cylinder bore diameter, stroke, and various installation recesses) to allow economical production.

Thus, for known refrigerant compressors having different refrigerating capacities, within a compressor family the differing heights of the electric drive units would result in a respectively different overall height of each individual refrigerant compressor. As a result, for small electric drive units the cylinder housing provided on the electric drive unit would be situated lower in the outer housing, with the risk that the overall height would be so greatly reduced that the refrigerant compressor could tip over or at least tilt in the outer housing, which in turn would require the outer housing to be correspondingly reduced in size, which is unacceptable for the economic reasons mentioned.

Therefore, it is known from the prior art to provide height compensation elements which balance out the differing heights of the electric drive units of refrigerant compressors in a compressor family in order to keep the overall height of the individual refrigerant compressors constant and to always allow use of the same outer housing.

These known height compensation elements are generally support elements together with springs mounted on the underside of the core stack which have different heights, depending on the height of the core stack. The smaller the electric drive unit that is used, the greater the overall height of the height compensation elements must be to keep the overall height of the refrigerant compressor essentially constant, wherein the height of springs as well as support elements may be varied to change the overall height of the height compensation elements.

Besides maintaining the overall height of the refrigerant compressors within a compressor family, the height compensation elements also allow identical crankshafts to be used in every case for each member of a compressor family, due to the fact that the height compensation elements consistently keep the cylinder housing, which has the main bearing for the crankshaft, at the same distance from the base of the outer housing, regardless of the height of the electric drive unit situated between the cylinder housing and the base of the outer housing. In this manner crankshafts of the same length may be used in all cases. Without the height compensation, due to the smaller distance between the cylinder housing and the base of the outer housing it would also be necessary to use shorter crankshafts for refrigerant compressors having smaller electric drive units.

Under these constraints, in the dimensioning of a refrigerant compressor it is always the objective to dimension the main bearing length in such a way that it has the greatest length possible in order to minimize the bearing load. The same as for the overall crankshaft, it is also true for the main bearing length that for economic reasons, within a compressor family the same main bearing length is provided so that the main bearing for any crankshaft in a compressor family may be machined in the same manner.

However, for known refrigerant compressors or compressor families having height compensation elements situated beneath the electric drive unit it has proven to be disadvantageous that, because the electric drive unit can increase in size only downward in the direction of the base of the outer housing, there are limitations in dimensioning the main bearing length, and for the respective largest compressor in a compressor family, although a larger main bearing length might be theoretically possible, for a compressor of the compressor family having a smaller electric drive unit this would not leave enough space on the crankshaft for the shrink fit between the crankshaft and the rotor.

Thus, although it is desirable and for larger electric drive units is also possible in principle, the main bearing cannot be further lengthened, and therefore the bearing load cannot be further reduced.

At the same time, since known refrigerant compressors in a compressor family are able to increase in size only in the downward direction, in order to accommodate the larger electric drive unit between the main bearing of the crankshaft and the oil sump the main bearing, in particular the lower main bearing, must also be situated at a sufficient height within the housing. The section of the crankshaft located beneath the lower main bearing must therefore be long enough to still be able to submerge into the oil sump at the base of the outer housing in order to convey the oil to the lubrication points.

However, in this lower section of the crankshaft oil is conveyed by means of an eccentric borehole in the crankshaft, in which the oil moves from the oil sump in the direction of the bearing section as a result of the rotation of the crankshaft. However, the conveying capacity of the eccentric borehole decreases with increasing length of the eccentric borehole, so that in this case for particularly large and therefore high electric drive units, this may result in impairment of the oil supply to the bearing section of the crankshaft and to the connecting rod and piston.

The object of the present invention, therefore, is to avoid these disadvantages and provide a refrigerant compressor of the type mentioned at the outset which, regardless of the height of the electric drive unit used, ensures a stable oil supply to the moving parts by always keeping the pump height as low as possible relative to the bearing section of the crankshaft.

A further aim of the present invention is to provide a compressor family of the type mentioned at the outset in which for each family member, regardless of the refrigerating capacity, the greatest possible main bearing length may be provided, based on the largest electric drive unit used.

A further aim of the present invention is to provide a refrigerant compressor of the type mentioned at the outset which, regardless of the height of the electric drive unit used, always has an essentially constant height.

This is achieved according to the invention by the characterizing features of claim 1.

For a refrigerant compressor having an electric drive unit, a cylinder housing, a crankshaft which may be driven by the electric drive unit, and a piston, driven by the crankshaft and guided in the cylinder housing, which compresses the refrigerant, it is provided that at least one height compensation element is situated between the cylinder housing and the electric drive unit. This allows the electric drive unit to be increased in size upwardly in the direction of the cylinder housing while at the same time the main bearing is situated as low as possible in the vicinity of the oil sump. In this case the main bearing length may be dimensioned on the basis of the largest electric drive unit, thus minimizing the bearing load and the losses from friction within a compressor family.

According to one preferred design variant of the invention, the cylinder housing has at least one contact flange which is mounted on at least one corresponding contact surface of the electric drive unit, and the at least one height compensation element is situated between the contact flange and the contact surface.

According to a further preferred design variant of the invention the electric drive unit is a single phase asynchronous motor, and the contact surface is the core stack of the stator of the single phase asynchronous motor.

The contact flange, contact surface, and height compensation element are preferably connected to one another by a screw connection which is preferably guided in a borehole or another type of recess in the height compensation element.

The object of the present invention is further achieved by the characterizing features of Claim 6, in which for a compressor family wherein each refrigerant compressor in the compressor family includes an electric drive unit, a cylinder housing, a crankshaft which may be driven by the electric drive unit, and a piston, driven by the crankshaft and guided in the cylinder housing, which compresses the refrigerant, and wherein the electric drive unit of each refrigerant compressor in the compressor family has a different height, composed of the height of the electric drive unit and the height of the cylinder housing (without height compensation elements), depending on the refrigerating capacity and the efficiency, it is provided that at least one height compensation element is situated between the electric drive unit and the cylinder housing of each refrigerant compressor. In this manner the distance between the lower edge of the section of the electric drive defining the height and the axis of the cylinder housing is set to be essentially identical for each compressor, and the overall height is kept constant, and it is possible for the electric drive unit to increase in size upwardly in the direction of the cylinder housing while at the same time the main bearing is situated as low as possible in the vicinity of the oil sump. In this case the main bearing length may be dimensioned on the basis of the largest electric drive unit, thus minimizing the bearing load and the friction losses within a compressor family.

In one preferred design variant of the invention the height of the section defining the electric drive is the height of the core stack of the stator.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail with reference to exemplary embodiments. The drawings show the following:

FIG. 1 shows a refrigerant compressor according to the prior art, in an isometric view;

FIG. 2 shows a refrigerant compressor according to the prior art, in a sectional view;

FIG. 3 shows a refrigerant compressor having a high refrigerating capacity and a large drive unit according to the prior art;

FIG. 4 shows a refrigerant compressor having a lower refrigerating capacity and a small drive unit according to the prior art;

FIG. 5 shows a schematic view of a refrigerant compressor according to the prior art, corresponding to FIG. 3;

FIG. 6 shows a schematic view of a refrigerant compressor according to the prior art, corresponding to FIG. 4;

FIG. 7 shows a crankshaft in detail;

FIG. 8 shows a schematic view of a refrigerant compressor according to the invention having a small drive unit;

FIG. 9 shows a schematic view of a refrigerant compressor according to the invention having a larger drive unit;

FIG. 10 shows an isometric view of a refrigerant compressor according to the invention;

FIG. 11 shows an isometric view of a height compensation element according to the invention;

FIG. 12 shows an isometric view of a height compensation element according to the invention;

FIG. 13 shows a detailed sectional view of a height compensation element according to the invention; and

FIG. 14 shows an isometric view of an alternative design variant of a height compensation element according to the invention.

EXEMPLARY EMBODIMENT OF THE INVENTION

FIG. 1 shows a refrigerant compressor according to the prior art in an isometric illustration, comprising a cylinder housing 1 and an electric drive unit, of which the core stack 2 and the winding heads 3 a, 3 b are schematically shown in FIG. 1, and height compensation elements, of which the coil spring elements 4 are visible, which are also used for elastic bearing of the refrigerant compressor. For the sake of clarity the outer housing is not shown in FIG. 1.

The cylinder housing 1 has multiple contact flanges 5 which extend in the direction of the crankshaft axis 6 and stand on the core stack 2. The cylinder housing 1 and the core stack 2 are fixedly joined together by screws, not visible in FIG. 1, which penetrate the core stack 2 from below and end in threaded boreholes present in the contact flanges 5.

FIG. 2 shows a sectional view of a refrigerant compressor according to FIG. 1, together with the outer housing 10 which is composed of two hermetically sealed housing halves 10 a, 10 b which are joined together. FIG. 2 also shows the crankshaft 11, which drives the piston 12 via a connecting rod 13. The crankshaft is supported in a section of the cylinder housing 1 referred to as the main bearing 14, and is mounted on a rotor 15 for the electric drive unit, preferably by means of a press fit.

Also shown in FIG. 2 is a connecting flange 16, mounted on the outer housing 10, for electrical lines, a suction muffler 17 provided on the cylinder head, and support feet 19 used for fixing the outer housing 10 to an external contact surface.

FIG. 3 shows a sectional view of a refrigerant compressor according to the prior art, wherein the upper half 10 a of the outer housing has been omitted. Clearly shown are the boreholes 7 in the core stack 2 and in the contact flanges 5, as well as the screws extending therein which are used for connecting the core stack 2 and the cylinder housing 1.

It is immediately apparent that the overall height H₁ of the refrigerant compressor is composed of the height H_(z1) of the cylinder housing 1, which extends from the lowest end of the contact flanges 5 to the piston axis 24, and the height of the electric drive unit, which is specified by the height H_(e1) of the core stack 2, for which reason the terms “core stack” and “electric drive unit” are used synonymously below.

As shown in particular in FIG. 2, the outer housing 10 is matched to the refrigerant compressor in such a way that the upper housing half 10 a extends to just above the cylinder housing 1, and in the region of the electrical connecting flange 16 extends downward in the direction thereof. To avoid having to produce different outer housings 10 for refrigerant compressors of differing refrigerating capacities in a compressor family, the outer housing in a compressor family is always dimensioned according to the refrigerant compressor having the greatest power.

The aim is to ensure that even refrigerant compressors having lower power, and therefore lower height, always occupy an essentially identical position within the outer housing 10 so that the connection of the electrical lines as well as the pressure and suction lines, and the positioning of the suction muffler, likewise do not have to be modified, and to prevent these smaller compressors inside the housing from tipping over or sliding out from the inner support due to vibration or acceleration during transport.

For this purpose height compensation elements are provided, for example in the form of support elements 8 and 9, which are surrounded by a coil spring element 4 situated beneath the electric drive unit 2, for example on the underside of the core stack 2, and on which the refrigerant compressor is supported.

The height of a height compensation element is thus composed of the overall height of the support elements 8, 9 which results under load from the refrigerant compressor, together with the surrounding coil spring element 4.

FIG. 4 shows a refrigerant compressor of the same design as in FIG. 3 according to the prior art, but with a lower refrigerating capacity. This is identifiable on the one hand by the lower height H_(e2) of the core stack 2, and on the other hand by the lower height H_(z2) of the cylinder housing 1 due to the different borehole diameter, and thus a lower overall height H₂. To keep the position of the piston axis 24 within the outer housing 10 the same as that of the refrigerant compressor illustrated in FIG. 3, height compensation elements composed of the support elements 8, 9 and the coil spring elements 4, having the same design as described in FIG. 3, are provided, but with the difference that they have a greater height H_(h2) than height H_(h1) of components 4, 8, 9 which form the height compensation elements in FIG. 3.

FIG. 5 shows a purely schematic view of a refrigerant compressor according to the prior art corresponding to FIG. 3, having the largest electric drive unit 2 of a compressor family, and FIG. 6, having the smallest electric drive unit 2 of the same compressor family. It is immediately apparent that in both cases the main bearing length H_(L) and the bearing width B_(L) are identical, so that the larger electric drive unit 2 in FIG. 5 reduces the distance between the compressor and the oil sump 19 due to the fact that the overall height H_(overall) of the refrigerant compressor is limited by the height of the outer housing.

As likewise shown in FIG. 5, the main bearing length H_(L) of this compressor could be increased, thereby reducing the bearing load, or the bearing load could be kept the same while reducing the friction losses. The press fit length P_(L) of the mounting for the rotor 15 on the crankshaft 11 would be smaller in this case, but would still be adequately dimensioned; in other words, the press fit length P_(L) in FIG. 5 is unnecessarily large, and it would be advantageous to increase the main bearing length H_(L) in order to reduce the bearing forces and achieve smaller friction losses.

However, if the main bearing length H_(L) were increased, for smaller compressors in the same compressor family as shown in FIG. 6 the necessary smallest possible press fit length P_(Lmin) could not be maintained.

The oil conveying height H_(oil) (not including the submersion depth E_(t)) relative to the lower main bearing 18 is therefore unnecessarily high in known refrigerant compressors in order to provide space for the largest electric drive unit 2 in a compressor family, although as shown in FIG. 6, the lower main bearing 18 could in fact be situated closer to the oil sump 19.

For better understanding FIG. 7 shows a crankshaft in detail, with a lower main bearing 18 and an upper main bearing 20, in addition to the oil inlet borehole 21 which is continuously immersed in the oil sump 19 and conveys the oil to the lower main bearing 18, from which location it is conveyed via an oil conveying spindle 22 to the upper main bearing 20, and from there to the oil outlet 23.

As previously mentioned, the oil is conveyed between the oil entry borehole 21 and the lower main bearing 18 via an eccentric borehole within the crankshaft 11, wherein the delivery height, i.e., the distance between the oil inlet borehole 21 and the main bearing 18, is limited and depends, among other factors, on the diameter of the crankshaft 11.

FIG. 8 shows in a purely schematic manner a refrigerant compressor according to the invention, which differs from the refrigerant compressors according to the prior art shown in FIGS. 5 and 6 by the fact that at least one height compensation element 26 according to the invention is situated between the cylinder housing 1 and the electric drive unit 2, and the compressor bearing elements 25 for every refrigerant compressor in the same compressor family are always identical with respect to their height H_(h3), so that the distance between the lower surface of the stator stack 2 relative to the base of the outer housing 10 is always the same.

FIG. 8 shows, strictly by way of example, a refrigerant compressor having the smallest electric drive unit 2 in a compressor family. The height compensation elements 26 are provided to keep the overall height H_(overall) essentially constant for every refrigerant compressor in this compressor family.

Due to the configuration of the height compensation elements 26, such a refrigerant compressor according to the invention may be increased in size only upwardly; i.e., a larger electric drive unit 2 does not reduce the distance between the lower surface of the stator stack 2 and the base of the outer housing 10.

FIG. 9 likewise shows in a purely schematic manner such a refrigerant compressor having the largest electric drive unit in a compressor family. In this case height compensation elements 26 are not provided, since the larger electric drive unit 2 has spanned this distance and is increased in size in the upward direction.

The lower main bearing 18 may therefore be situated as low as possible in the outer housing 11, since it is necessary to ensure only that the compressor does not brush against the housing wall 10 during operation, in particular during start-up.

At the same time, the main bearing length H_(L) may be dimensioned on the basis of the largest electric drive unit 2, as illustrated in FIG. 9, since the press fit length P_(L) is always the same, regardless of the size of the electric drive unit 2. Thus, in contrast to the prior art the bearing load of each compressor in a compressor family may be reduced.

FIG. 10 shows an isometric view of a refrigerant compressor according to the invention together with height compensation elements 26, a detailed view of which is shown by way of example in FIG. 11. Based on the above discussion, the height compensation element 26 illustrated as an example in FIG. 11 may have a different shape, and in the shape illustrated represents only one of many possible embodiments. An alternative embodiment is shown in FIG. 12 or FIG. 14, for example.

FIG. 13 shows a sectional view of a height compensation element 26 according to the invention in the installed position.

FIG. 14 shows an isometric view of an alternative design variant of a height compensation element 26 according to the invention, without a borehole but with a recess for accommodating the connecting screw.

The dimensions and proportions of the individual components relative to one another are illustrated in a purely schematic manner.

LIST OF REFERENCE NUMERALS

-   -   1 Cylinder housing     -   2 Core stack of the electric drive unit     -   3 Winding head     -   4 Coil spring element     -   5 Contact flange     -   6 Crankshaft axis     -   7 Borehole in the core stack     -   8 Support element     -   9 Support element     -   10 Outer housing     -   11 Crankshaft     -   12 Piston     -   13 Connecting rod     -   14 Main bearing     -   15 Rotor     -   16 Connecting flange for electrical lines     -   17 Suction muffler     -   18 Lower main bearing     -   19 Oil sump     -   20 Upper main bearing     -   21 Oil pump inlet borehole     -   22 Oil conveying spindle     -   23 Oil outlet     -   24 Piston axis     -   25 Compressor bearing element     -   26 Height compensation element according to the invention 

1: Refrigerant compressor, comprising an electric drive unit (2), a cylinder housing (1), a crankshaft (11) which may be driven by the electric drive unit, wherein the cylinder housing (1) comprises the main bearing for the crankshaft (11), and a piston (12), driven by the crankshaft (11) and guided in the cylinder housing (1), which compresses the refrigerant, wherein at least one height compensation element (26) is situated between the cylinder housing (1) and the electric drive unit (2), in order to keep an overall height of the cylinder housing and the respective drive unit practically identical within a compressor family having drive units of different heights. 2: Refrigerant compressor according to claim 1, wherein the cylinder housing (1) has at least one contact flange (5) which is mounted on at least one corresponding contact surface of the electric drive unit (2), and the at least one height compensation element (26) is situated between the contact flange (5) and the contact surface. 3: Refrigerant compressor according to claim 2, wherein the electric drive unit is a single phase asynchronous motor, and the contact surface is the core stack (2) of the stator. 4: Refrigerant compressor according to claim 3, wherein the contact flange (5), height compensation element (26), and contact surface are screwed together. 5: Refrigerant compressor according to claim 1, wherein the height compensation element (26) has a borehole or recess for accommodating a fastening element, preferably a screw. 6: Compressor family having refrigerant compressors of different refrigerating capacities, wherein each refrigerant compressor includes an electric drive unit (2), a cylinder housing (1), a crankshaft (11) which may be driven by the electric drive unit (2), wherein the cylinder housing (1) has the main bearing for the crankshaft (11), and a piston (12), driven by the crankshaft (11) and guided in the cylinder housing (1), which compresses the refrigerant, wherein the electric drive unit (2) of each refrigerant compressor in the compressor family has a different overall height (H_(overall)), composed of the height of the electric drive unit (H_(e)) and the height of the cylinder housing (H_(z)), depending on the refrigerating capacity, wherein at least one height compensation element (26) is situated between the electric drive unit (2) and the cylinder housing (1) of each refrigerant compressor in the compressor family. 7: Compressor family according to claim 6, wherein the section defining the height (H_(e)) of the electric drive unit (2) is the height of the core stack (2) of the stator. 